Flow characteristics of waxy petroleum residuum



United States Patent Ofilice 3,248,186 Patented Apr. 26, 1966 3,248,186 FLOW CHARACTERISTICS OF WAXY PETROLEUM RESIDUUM Darrell Brownawell, Scotch Plains, and Harold N. Miller,

Plainfield, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Sept. 12, 1962, Ser. No. 223,252

. 3 Claims. (Cl. 44-62) A typical Zelten residuum, which boils above 680 F.,

contains about wt. percent wax and has a flow point of 105 F. This wax includes waxes of relatively high molecular weight ranging from about C to C paraflins which gives rise to a number of problems in transporting and storing this kind of heavy oil. Even though this kind of oil has a relatively low viscosity as measured by conventional methods compared to heavy oilsof low wax content, the handling of the high wax content residuum creates special difliculties on account of the manner in which the oil undergoes changes in flow characteristics on being subjected to changes in temperature. Generally, the standardized ASTM pour point is reasonably indicative of how low the temperature of an oil can be decreased to the point at which it can be satisfactorily made to flow. However, with high waxy residua, such as a Zelten oil, the pour points determined by the standardized procedure are variable and a function of prior thermal treatment. Thus, it was found necessary to alter the standard ASTM pourpoint procedure to obtain a reproducible and more meaningful measure of flow characteristics in testing the high wax-containing residual oils, such as in Zelten crude residuum. In this flow point test, a sample of oil is first heated to 200 F., then cooled to 32 F. before it is again heated to an intermediate temperature in the range of 90 to 200 F. for testing under the standard ASTM procedure. By putting the oil through a temperature cycle series, such as mentioned, a determination is made of the flow point corresponding to the maximum pour point in the series, and such a flow point is the best measure so far achieved in determining how well such oils can be kept fluid in storage and for pumping or transporting.

In making the discovery of the present invention, a number of conventional pour point depressing compounds, such as shown in the prior art for use in lubricating oils and distillate oils, were tried and found to be quite unsuitable. Such conventional pour point depressants are typified by polymer compounds such as chlorinated waxnaphthalene condensation polymers made from waxes having varying carbon chains varying from about 16 to 24 carbon atoms, acyl polystyrenes in which the acyl group contains fewer than 18 carbon atoms, alkylated polystyrenes having as many as 22 carbon atoms in the alkyl group, and polyvinyl stearate. While some of the aforementioned polymers give some lowering of the flow point in the high wax-containing residua using the ordinary ASTM pour point method or even a single heating treatment, they were found to be unsuitable when the oil was put through a second thermal cycle which involved reheating the oil containing the additive to various temperatures up to temperatures of 200 F.

In accordance with the present invention, a surprisingly enhanced flow point characteristic was found to be given to the high wax-containing residual oils by blending with these oils certain small amounts of acyl polystyrenes having 20 to 22 carbon atoms in the acyl group, the acyl group thus approximating arachidic and behenic acids in length, i.e. and and mixtures thereof. It was determined also important to use concentration ranges of this kind of acyl polystyrene, and preferably from 0.1 to 1.0 wt. percent, for the best results.

In general, polyacylated polystyrenes are assigned the following structure:

wherein the acyl group is defined as containing a straight chain alkyl group R of at least 19 carbon atoms, and subscript n is a number from 2 to 50 of the recurring'units of the acylated polystyrene. For the purposes of the present invention, the acyl group which makes the acyl polystyrene potent for improving the flow characteristics of a high wax-containing residual contains at least 20 up to 30 carbon atoms, and preferably 20 to 22 carbon atoms. It appears that these particular' compounds have never before been produced. The method of forming these acyl polystyrenes comprises dissolving commercial polystyrene in o-dichlorobenzene and adding to this solution 0.5 to 1.0 mole of a carboxylic acid chloride-aluminum chloride complex. styrene units to acyl units in the acyl polystyrene can vary from 1:1 to 2:1. This complex is formed by mixing equirnolar amounts of aluminum chloride with the carboxylic acid chloride dissolved in o-dichlorobenzene at a temperature of 20 to 70 C. After all the acid chloride-aluminum chloride complex has been added to the solution of the polystyrene and hydrogen chloride evolution has stopped, the aluminum catalyst is destroyed by addition of water or alcohol to the reaction mixture. The acylated polystyrene is then taken up in a suitable hydrocarbon solvent, such as heptane or kerosene, and washed with an aqueous alkaline solution and Water. The solvent may be evaporated to isolate the polymer or the polymer may be dissolved in the solvent for blending with the residual oil.

The high molecular Weight acylating reactants that are of particular interest and use for the purpose of the present invention are the C and C acid chlorides, or mixtures including these two acid chlorides, obtained from straight chain carboxylic acids, such as arachidic and behenic acid, or commercial acid mixtures including these two. These acid chlorides are obtained by treating the corresponding acid dissolved in a suitable solvent, such as o-dichlorobenzene, with chlorinating agents, such as phosphorus tn'chloride. The reaction temperature is maintained at 20 to C.

7 It was found that in order to achieve proper dispersion of the acyl polystyrenes in the high boiling and high waxcontaining residua, that the blending and mixing should take place with the oil heated to an elevated temperature The ratio of in the range of 100 to about 250 F., to melt the waxes and thus obtain homogeneous dispersion. In determining the fiow points of the blends, duplicate tests were made; each blend was put through at least two thermal cycles to find out whether the changein flow TABLE II Processing Zelten crudes Heavy Fuel Oil Inspections Zelten Aramco Kuwait Target Vol. percent 680 V. VT+ on crudc 35 39 47 Inspections on 680' r. VT+:

Gravity, API 22 15 14 Sulfur, Wt. percent 0. 4 3.0 4. 2 3.

Viscosity, SF 122 F 65 110 340 40-175 MNI, wt percent 2.3 4. 3.8

Conradson carbon, wt percen 4. 5 8-9 10-11 Flow 12., F 105 65 55 75 Hot filtration sed., wt percent 0. 01 0. 02 0. 02 0.

1 maximum.

additives on the flow points of the high wax-containing residuum are shown below:

TABLE I Efiect of additives on flow points of 680 F.|-

virgin Zelten residuum The inspection shown in the foregoing Table II shows that the Zelten residuum is a premium product per se,

or for blending to improve other heavy fuel oils with respect to its low sulfur content, low viscosity, low MNT (modified naphtha insolubles), and low Conradson car- Furthermore, it is very low in ash and vanadium. These qualities also make the Zelten crude residuum anbon.

excellent cracking stock and for obtaining various valu- Additive Additive wt. E. Lower F., Upper percent cone. flow 1 flow 2 680 I .+Virgin zelten residuum None 95 100 N one 100 100 C1 Acyl polystyrene 1.0 75 75 0. 1 100 100 1. 0 65 Cm Acyl polystyrene 0. 3 0. 1 2. 0 65 65 C Acyl polystyrene 1. 0 55 60 0. 3 55 55 0. 1 1. 0 65 70 Mixed Cao-Caz acyl polystyrene 8.? 2(5) Wax-naphthalene condensate (from 135 1. 0 100 105 F., M.P. wax) 0.3 100 105 0. 1 100 100 Wax-naphthalene condensate (from 180 1. 0 65 100 F., M.P. wax) 0.3 55 100 0. 1 55 100 1. 0 90 C22 Alkyl polystyrene 0. 3 100 100 0. 1 95 1. 0 100 Polyvinyl stearate O. 3 100 100 0. 1 100 1 Lower flow point thermal cycle, 200 F. 32 F. 200 F. 1ower flow point. 2 Upper flow point thermal cycle, 200 F. 32 F. F. upper flow point.

It can be seen from the data in the above table that wt. percent at which concentration, there appears to oc- 70 cur the formation of stable aggregates of the additive with wax in the oil if the blending and mixing of the additive has been properly carried out.

The Zelten residuum boiling above 680 R, which typifies the kind of high wax-containing oils to be im- 75 able products, such as straight chain olefins.

-which it is desired to make using the Zelten residuum as a blending stock provided one can lower the flow point. For example, it is desired to mix the Zelten crude in a 50/50 mixture with the Aramco or Kuwait residuum. Of course, such a blending lowers the wax content, but evenso, the flow point may not be sufliciently reduced without using the specially adapted C acyl polystyrenes as additives in suitable concentration for lower.-.

ing the flow point back to below the 75 F. target. For example, in the 50/50 Zelten/Aramco blend, the addition of only 0.15 wt. percent of C acyl polystyrene wasfound sufficient to meet the target of a 75 F. flow point,

the 50/50 mixture without this additive having a flow.

point of 95 F. Thus, the proportion of additive with The column under the notation Target indicates types of blends" respect to the Zelten residuum in the blend is 0.3 wt. percent. In other words,the concentration of the C acyl polystyrene additive required for the desired improvement of fluidity can be based on the proportion of the high wax-containing oil component.

The invention described is claimed as follows:

1. A petroleum residuum oil composition having improved characteristics,'which comprises essentially a high wax content petroleum residuum boiling above about 650 F. and having a flow point and a pour point above 75 F., improved with respect to its flow characteristics by incorporating and blending therewith an amount of about 0.1 to 1.0 wt. percent of C to C acyl polystyrene having the acyl group wherein R is a straight chain alkyl group containing from 19 to 21 carbon atoms, the number of styrene units in the acyl polystyrene is 2 to 50, and the ratio of styrene units to acyl units present in the acyl polystyrene varies from 1:1to2z1.

2. Oil composition as defined by claim 1 wherein the amount of acyl polystyrene present is in the range from 0.1 to 0.3% by weight.

-3. An improved composition of petroleum crude oil containing high melting paraflins of to carbon atoms per molecule and having a natural flow-point above F. to which has been added a minor proportion, not exceeding 1% by weight and sufiicient to lower the flowpoint of said oil below 75 F., of a C C acyl polystyrene having the acyl group wherein R is a straight chain alkyl group containing from 19 to 21 carbon atoms, the number of styrene units in the acyl polystyrene is 2 to. 50, and the ratio of styrene units to acyl units present in the acyl polystyrene varies from 1:1to 2:1.

References Cited by the Examiner v UNITED STATES PATENTS 2,642,398 6/ 3' Butler 25252 2,703,817 3/ 1955 Serniuk 260592 3,069,245 12/ 1962 Wythe et a1. 44-62 DANIEL E. WYMAN, Primary Examiner. 

1. A PETROLEUM RESIDUUM OIL COMPOSITION HAVING IMPROVED CHARACTERISTICS, WHICH COMPRISES ESSENTIALLY A HIGH WAX CONTENT PETROLEUM RESIDUUM BOILING ABOVE ABOUT 650*F. AND HAVING A FLOW POINT AND A POUR POINT ABOVE 75*F., IMPROVED WITH RESPECT TO ITS FLOW CHARACTERISTICS BY INCORPORATING AND BLENDING THEREWITH AN AMOUNT OF ABOUT 0.1 TO 1.0 WT. PERCENT OF C20 TO C22 ACYL POLYSTYRENE HAVING THE ACYL GROUP. 